AbstractID: 5207 Title: Optimizing dose and image quality in pediatric computed
tomography
Purpose: The goal of this work was to accurately quantify the doses delivered to
pediatric patients during computed tomography (CT) exams while simultaneously
evaluating the image quality of images obtained with the same protocols, and thus
identify potential dose-saving protocols that maintain adequate image quality.
Method and Materials: A tomographic newborn physical phantom was constructed
from tissue-equivalent materials for use in evaluating the doses delivered to pediatric
patients as a result of diagnostic imaging. Fiber optic-coupled (FOC) dosimeters were
used along with the physical phantom to measure average organ doses during CT exams
across a wide range of protocol parameters (80-120 kV, 50-150 mAs, 12 mm and 24 mm
collimated beam widths, pitches of 0.75, 1.0, and 1.25, for both head and body protocols).
Then, images of the Catphan CTP515 low contrast module were acquired using the same
protocols, and scored automatically with a custom-written scoring routine with threshold
contrast-to-noise ratios (CNR) based on radiologists’ scoring of similar phantom images.
Results: Measured effective dose values for head exams ranged from 0.33 mSv to 4.3
mSv, depending on protocol selection. These effective dose values are driven by doses to
the bone marrow, bone surface, brain, and thyroid gland. Measured effective doses for
CAP exams ranged from 1 mSv to 14.3 mSv, depending on protocol selection. A
collimated beam width of 24 mm (16 x 1.5) was determined to be the optimal setting for
both head and CAP imaging in terms of both image quality and dose.
Conclusions: Tube potential and tube current-time product are the two major
contributors to both dose and image quality. However, the use of pitch values less than
1.0 does involve a substantial dose penalty (approximately 30 percent greater dose)
without providing any significant gains in image quality for general imaging tasks.